Research On Mixed Spectrum Handoff Strategy Based On Spectrum Prediction In Cognitive Radio

Radio spectrum is a non-renewable and precious resource. With the rapid development of wireless communication, the traditional static spectrum allocation couldn’t satisfy the gradually increasing of users’ communication demands. Accordingly, it is extremely necessary to adopt a dynamic and efficient spectrum assignment scheme. Cognitive radio is conceived as a promising solution to the spectrum scarcity problem to enhance the spectrum utilization by enabling unlicensed users to exploit the unused spectrum dynamically.Due to the licensed users or Primary Users, who had paid licensing fees for the spectrum, are the purchasers of frequency resource, the quality of PUs’ communication service must be ensured. Unlicensed users access the spectrum holes temporarily. The Second users must vacate the licensed spectrum no matter when and where the Primary User reuses the current spectrum, to ensure it couldn’t cause interference to PU’s transmissions. So, in order that SUs can continue to transmit, they must detect available spectrum and switch to a suitable channel smoothly and promptly.Because of the randomness of the PUs’ reappearance in the realistic wireless communication environment, the disruptions to both PUs and SUs are difficult to prevent. In a cognitive radio networks, SUs face transmission interruptions whenever necessary. To eliminate collisions among the two kinds of users and protect the quality of service, this paper explore the spectrum handoff caused by PUs reuse the licensed spectrum, and the two main contents are the selection of the target channel and the condition of switching channels.As a key technology of the cognitive radio, spectrum handoff has attracted extensive attention from the academia and the industry since it was proposed. First of all, we introduce the concept of the spectrum handoff technology in cognitive radio network. And then, we study on the working mode of cognitive node and constructed the random channel as an ON-OFF based on observing the characteristics of the PUs’ activity. Based on existing researches of the idle time estimation, we propose spectrum handoff frameworks based on the improved estimation algorithm. The simulation results show that the approach based on the channel prediction outperforms the conventional random reactive scheme in terms of a fewer collision probability.In order to reduce the number of handoff reasonably, we combine the task allocation threshold model of swarm intelligence system with the idle time estimation algorithm based on the analogy analysis. And then we propose a mixed spectrum handoff strategy which is more suitable for the distributed cognitive radio network. In this scheme, SUs could achieve dynamically performing spectrum switching as required. As compared with other spectrum handoff schemes, the simulation results show that the number of SU’s handoff and the time of SUs’ transmission have been reduced in this algorithm.